Fix Dart Freezed naming for nested objects

Fixes glideapps#2660

Modify the naming convention for nested objects in Dart Freezed class generation to include the parent object name.

* **DartRenderer.ts**
  - Update `dartType` method to include the parent object name for nested objects.
  - Adjust `emitFreezedClassDefinition` and `emitClassDefinition` methods to handle the new naming convention for nested objects.
  - Modify `_emitVariables` method to use the new naming convention for nested objects.

* **parser.dart**
  - Add tests for the new functionality to ensure nested objects include the parent object name.
  - Implement `testNestedObjectNaming` function to validate the new naming convention for nested objects.

TODO:

- [ ] Make sure tests work
- [ ] Make sure this offers backwards compatibility

---

For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/glideapps/quicktype/issues/2660?shareId=XXXX-XXXX-XXXX-XXXX).

packages/quicktype-core/src/language/Dart/DartRenderer.ts

@@ -192,7 +192,7 @@ export class DartRenderer extends ConvenienceRenderer {
         this.emitLine("}");
     }
 
-    protected dartType(t: Type, withIssues = false, forceNullable = false): Sourcelike {
+    protected dartType(t: Type, withIssues = false, forceNullable = false, parentName?: Name): Sourcelike {
         const nullable =
             forceNullable || (this._options.nullSafety && t.isNullable && !this._options.requiredProperties);
         const withNullable = (s: Sourcelike): Sourcelike => (nullable ? [s, "?"] : s);
@@ -205,7 +205,10 @@ export class DartRenderer extends ConvenienceRenderer {
             _doubleType => withNullable("double"),
             _stringType => withNullable("String"),
             arrayType => withNullable(["List<", this.dartType(arrayType.items, withIssues), ">"]),
-            classType => withNullable(this.nameForNamedType(classType)),
+            classType => {
+                const className = parentName ? [parentName, "_", this.nameForNamedType(classType)] : this.nameForNamedType(classType);
+                return withNullable(className);
+            },
             mapType => withNullable(["Map<String, ", this.dartType(mapType.values, withIssues), ">"]),
             enumType => withNullable(this.nameForNamedType(enumType)),
             unionType => {
@@ -441,7 +444,7 @@ export class DartRenderer extends ConvenienceRenderer {
         this.ensureBlankLine();
     }
 
-    private _emitVariables(c: ClassType): void {
+    private _emitVariables(c: ClassType, parentName?: Name): void {
         this.forEachClassProperty(c, "none", (name, jsonName, p) => {
             const description = this.descriptionForClassProperty(c, jsonName);
             if (description !== undefined) {
@@ -458,7 +461,7 @@ export class DartRenderer extends ConvenienceRenderer {
                 this.emitLine(`@JsonKey(name: "${jsonName}")`);
             }
 
-            this.emitLine(this._options.finalProperties ? "final " : "", this.dartType(p.type, true), " ", name, ";");
+            this.emitLine(this._options.finalProperties ? "final " : "", this.dartType(p.type, true, false, parentName), " ", name, ";");
         });
     }
 
@@ -544,7 +547,7 @@ export class DartRenderer extends ConvenienceRenderer {
         this.emitLine("};");
     }
 
-    protected emitClassDefinition(c: ClassType, className: Name): void {
+    protected emitClassDefinition(c: ClassType, className: Name, parentName?: Name): void {
         this.emitDescription(this.descriptionForType(c));
         if (this._options.useHive) {
             this.classCounter++;
@@ -560,7 +563,7 @@ export class DartRenderer extends ConvenienceRenderer {
             if (c.getProperties().size === 0) {
                 this._emitEmptyConstructor(className);
             } else {
-                this._emitVariables(c);
+                this._emitVariables(c, parentName);
                 this.ensureBlankLine();
                 this._emitConstructor(c, className);
             }
@@ -601,7 +604,7 @@ export class DartRenderer extends ConvenienceRenderer {
         });
     }
 
-    protected emitFreezedClassDefinition(c: ClassType, className: Name): void {
+    protected emitFreezedClassDefinition(c: ClassType, className: Name, parentName?: Name): void {
         this.emitDescription(this.descriptionForType(c));
 
         this.emitLine("@freezed");
@@ -625,7 +628,7 @@ export class DartRenderer extends ConvenienceRenderer {
                             this.emitLine(`@JsonKey(name: "${jsonName}")`);
                         }
 
-                        this.emitLine(required ? "required " : "", this.dartType(prop.type, true), " ", name, ",");
+                        this.emitLine(required ? "required " : "", this.dartType(prop.type, true, false, parentName), " ", name, ",");
                     });
                 });
                 this.emitLine("}) = _", className, ";");
@@ -644,6 +647,13 @@ export class DartRenderer extends ConvenienceRenderer {
                 "FromJson(json);"
             );
         });
+
+        this.forEachClassProperty(c, "none", (name, jsonName, prop) => {
+            if (prop.type instanceof ClassType) {
+                const nestedClassName = [className, "_", this.nameForNamedType(prop.type)].join("");
+                this.emitFreezedClassDefinition(prop.type, nestedClassName, className);
+            }
+        });
     }
 
     protected emitEnumDefinition(e: EnumType, enumName: Name): void {

test/fixtures/dart/parser.dart

@@ -9,3 +9,25 @@ void main(List<String> arguments) async {
     stdout.write(result);
   });
 }
+
+void testNestedObjectNaming() {
+  final json = '''
+  {
+    "hello": "world",
+    "works": {
+      "yes": true,
+      "no": false
+    }
+  }
+  ''';
+
+  final fasfasfsa = Fasfasfsa.fromJson(jsonDecode(json));
+  assert(fasfasfsa.works is Fasfasfsa_Works);
+  assert(fasfasfsa.works.yes == true);
+  assert(fasfasfsa.works.no == false);
+}
+
+void main() {
+  testNestedObjectNaming();
+  print('All tests passed.');
+}